Method for surface modification of molded article of plastic and method for modifying polymer

ABSTRACT

An invented method for the surface modification of a molded plastic treats a molded plastic with an oxygen-atom-containing gas such as oxygen, carbon monoxide, a nitrogen oxide, or a sulfur oxide in the presence of N-hydroxyphthalimide or another imide compound represented by the following formula (1):                    
     wherein R 1  and R 2  are each, identical to or different from each other, a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, or an acyl group, or R 1  and R 2  may be combined to form a double bond or an aromatic or non-aromatic ring; X is an oxygen atom or a hydroxyl group. An invented method for modifying a polymer treats a polymer with an oxygen-atom-containing gas such as oxygen, carbon monoxide, a nitrogen oxide, or a sulfur oxide in the presence of the imide compound represented by the formula (1).

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP00/02255 which has an Internationalfiling date of Apr. 7, 2000, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a method for the surface modificationof a molded plastic, and specifically, it relates to a method for thesurface modification which imparts adhesion or adhesive property tocoating films, antistatic property and other characteristics to thesurface of the molded plastic, as well as to a surface-modified moldedplastic obtained by the method. The present invention also relates to amethod for modifying a polymer, and specifically it relates to a methodfor modifying a polymer, which can impart antistatic property and othercharacteristics to the polymer by the introduction of a polar group, aswell as to a modified polymer obtained by the method.

BACKGROUND ART

Many of resins for use in optical lenses, optical disks, and otheroptical materials require adhesion to coating films formed on thesurfaces thereof, in addition to a high transparency, a lowbirefringence, and other basic characteristics. Add to this, demands aremade on these resins to minimize changes due to environmental conditionsin optical characteristics (especially, refractive index) and indimension. Poly(methyl methacrylate) (PMMA), a typical transparentresin, is excellent, for example, in adhesive property and adhesion tocoating films, but highly absorbs moisture and therefore largely changesin refractive index, which causes changes in focal distance.Accordingly, PMMA cannot be used as optical lenses in, for example,cameras. In addition, PMMA greatly changes in dimension due to moistureabsorption, and when PMMA is applied to magneto-optic disks and otherapplications in which an inorganic film is applied thereon, theinorganic film cracks with dimensional change. A polycarbonate (PC)predominantly used for optical disks is relatively free from the aboveproblems but exhibits a high birefringence.

On the other hand, to solve the problems due to moisture absorption,polyolefin resins each having a non-aromatic ring introduced into aprinciple chain (trade names: APO and ZEONEX, etc.) have been reportedas optical material polymers in recent years. However, this resin has ahigh hydrophobicity which is a feature of polyolefin polymers, andtherefore has a problem of a low adhesion to coating films formed on thesurface. In order to solve this problem, a polyolefin resin (trade name:ARTON) having a polar group introduced into the non-aromatic ring is onthe market. However, this resin inevitably has a higher hygroscopicitythan a polyolefin resin having no polar group.

As is described above, the low water absorption which is required forensuring optical stability and dimensional stability, and thehydrophilicity which contributes to adhesion to coating films are intrade-off relationship. To make these two characteristics compatiblewith each other, it is ideal that the inside of a molded article such asa lens or disk substrate is made of a hydrophobic polymer having a lowhygroscopicity and the surface thereof alone is made of a hydrophilicpolymer having a satisfactory adhesion to coating films.

Generally, known methods for the surface modification of plastics are,for example, (i) a method of coating the surface with a surfactant, (ii)a method of activating the surface through corona discharge, and (iii) amethod of activating the surface though laser abrasion. However, themethod (i) is insufficient in adhesion to coating films, although it isuseful, for example, for imparting a temporary antistatic property. Themethods (ii) and (iii) invite fine projections and depressions on thesurfaces of plastics.

On the other hand, many of polymers for general use such aspolyethylenes, polypropylenes, and polystyrenes have no free polar groupor reactive functional group in a molecule and have a stronglyhydrophobic characteristic, and are therefore generally static-prone.Accordingly, these polymers are usually incorporated with antistaticagents prior to use. However, this technique often invites a problem ofbleeding out of the antistatic agents. The polymer itself must have apolar group to avoid this problem.

Generally, known methods for producing a polymer having a polar groupinclude, for example, (i) a method of copolymerizing a material with amonomer having a polar group in a polymerization step, (ii) a method ofconverting an inherently hydrophilic polymer such as cellulose acetateinto a hydrophobic polymer and then controlling the degree ofesterification thereof through deesterification (saponification), (iii)a method of converting an aromatic ring of a polymer having the aromaticring such as benzene ring into a functional group, and (iv) a method ofcombining a hydrophilic group such as carboxyl group with an unsaturatedmoiety of an aliphatic cyclic hydrocarbon polymer having theunsaturated-bond moiety such as dicyclopentadiene.

However, these methods are much limited in their application range. Forexample, a special monomer is required for converting an aromatic ringinto a functional group, or the method can be applied only to a specificpolymer previously having a functional group such as a hydroxyl group oran unsaturated moiety.

As a possible solution to the problems, there is a method of introducinga polar group into a principle chain through oxidization of, forexample, a polypropylene. However, according to conventional oxidationtechniques, the principle chain is liable to cleave to thereby yield alow molecular weight product.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide amethod for the surface modification of a molded plastic, which canimpart hydrophilicity only to the surface without significantly varyingthe water absorption of the molded plastic.

It is another object of the present invention to provide a method formodifying a surface of a plastic, which can hydrophilize only thesurface of a molded article made of a hydrophobic polymer to therebyimprove adhesion to coating films, adhesive property, and antistaticproperty.

A further object of the present invention is to provide a method for thesurface modification of a molded plastic, which can hydrophilize thesurface without causing projections and depressions on the surface.

Yet another object of the present invention is to provide asurface-modified molded plastic which is satisfactory in optical anddimensional stability and has excellent adhesion to coating films,adhesive property and a high antistatic property.

A still further object of the present invention is to provide aversatile method of modifying a polymer, which can easily introduce apolar group into a polymer, especially to a hydrophobic polymer.

It is another object of the present invention to provide a method formodifying a polymer, which can introduce a polar group into the polymerwithout cleaving a principle chain.

It is still another object of the present invention to provide a methodfor modifying a polymer, which can introduce a desired polar group intothe polymer in a desired proportion.

A yet further object of the present invention is to provide a polymerhaving a satisfactory antistatic property.

After intensive investigations to achieve the above objects, the presentinventors found that the treatment of a molded plastic with anoxygen-atom-containing gas in the presence of a specific catalyst canefficiently hydrophilize only the surface of the molded plastic, andthat the treatment of a polymer with an oxygen-atom-containing gas inthe presence of a specific catalyst can efficiently introduce a polargroup into the polymer. The present invention has been accomplishedbased on these findings.

Specifically, the present invention provides a method for the surfacemodification of a molded plastic. The method includes the step oftreating a molded plastic with an oxygen-atom-containing gas in thepresence of an imide compound represented by the following formula (1):

(wherein R¹ and R² are each, identical to or different from each other,a hydrogen atom, a halogen atom, an alkyl group, an aryl group, acycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group,an alkoxycarbonyl group, or an acyl group, or R¹ and R² may be combinedto form a double bond or an aromatic or non-aromatic ring; X is anoxygen atom or a hydroxyl group; and one or two of N-substituted cyclicimido group indicated in the formula (1) may be further formed on theR¹, R², or on the double bond or aromatic or non-aromatic ring formed byR¹ and R²).

As the oxygen-atom-containing gas, at least one gas selected fromoxygen, carbon monoxide, nitrogen oxides, and sulfur oxides can be used.

The present invention provides, in another aspect, a surface-modifiedmolded plastic obtained by treating a molded plastic according to theaforementioned method.

In a further aspect, the present invention provides a method formodifying a polymer, which includes the step of treating a polymer witha oxygen-atom-containing gas in the presence of the imide compoundrepresented by the formula (1).

At least one gas selected from oxygen, carbon monoxide, nitrogen oxides,and sulfur oxides can be used as the oxygen-atom-containing gas.

In yet another aspect, the present invention provides a modified polymerobtained by treating a polymer according to the aforementioned method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared absorption spectrum of a polymer (polystyrene)prior to modification in Example 7, and FIG. 2 is an infrared absorptionspectrum of a modified polymer in Example 7.

FIG. 3 is an infrared absorption spectrum of a polymer(cyclopentadiene-based polymer) prior to modification in Example 8, and

FIG. 4 is an infrared absorption spectrum of a modified polymer inExample 8.

FIG. 5 is an infrared absorption spectrum of a polymer[poly(3,5-dimethyladamant-1-yl methacrylate)] prior to modification inExample 9, and

FIG. 6 is an infrared absorption spectrum of a modified polymer inExample 9.

FIG. 7 is an infrared absorption spectrum of a polymer [poly(1-adamantylacrylate)] prior to modification in Example 10, and

FIG. 8 is an infrared absorption spectrum of a modified polymer inExample 10.

BEST MODE FOR CARRYING OUT THE INVENTION

In the invented method for the surface modification of a molded plastic,molded plastics to be treated include molded plastics made of a varietyof polymers each having a primary, secondary, or tertiary carbon atom ina principle chain or in a side chain. In the invented method formodifying a polymer, polymers to be treated include a variety ofpolymers each having a primary, secondary, or tertiary carbon atom in aprinciple chain or in a side chain.

Polymers constituting the molded plastics and polymers to be modifiedinclude, but are not limited to, polyethylenes (e.g., low-densitypolyethylene, linear low-density polyethylene, and metallocene-catalyzedpolyethylene), ethylene copolymers (e.g., ethylene-vinyl acetatecopolymers, ethylene-acrylic ester copolymers, ethylene-methacrylicester copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylicacid copolymers, and ionomers), polypropylene, ethylene-propylenecopolymers, poly-1-butene, poly(4-methylpentene) (TPX), polyisobutylene,and other olefinic resins; polybutadiene, polyisoprene,butadiene-styrene copolymers, butadiene-propylene copolymers,butadiene-acrylonitrile copolymers, isoprene-styrene copolymers, andother diene-based resins; ring-opened polymers or hydrogenated productsthereof, of cyclic olefins such as cycloolefins (e.g., cyclobutene,cyclopentene, cycloheptene, cyclooctene, 3-methylcyclooctene,cyclooctadiene, cyclodecene, 3-methylcyclodecene, cyclododecene, andcyclododecatriene), norbornene derivatives, tetracyclododecene, andproducts from Diels-Alder reaction between dicyclopentadiene and a(meth)acrylic ester; copolymers of the cyclic olefins with ethylene andthe other olefins; polystyrene, styrene-acrylonitrile copolymers,styrene-acrylonitrile-butadiene copolymers, poly(α-methylstyrene), andother polymers each containing an aromatic vinyl compound as a monomericcomponent; polymers each containing, as a monomeric component, analicyclic vinyl compound such as vinylcyclohexane, vinylcyclohexene,vinyladamantane, vinylnorbornane, and vinylnorbornene; vinylchloride-based resins; vinylidene chloride-based resins; vinylacetate-based resins; cellulosic resins; polyethers; a variety ofpolyesters formed by polycondensation of a dibasic acid with a glycol;polyamides; and acrylic resins each containing an acrylic compound suchas a (meth)acrylic ester as a monomeric component. The ring-openedpolymers of cyclic olefins can be obtained by metathesis polymerization.

Of these polymers, preferred are hydrocarbon polymers having a saturatedcarbon chain as a principle chain, such as (A1) polyethylenes (e.g.,low-density polyethylene and metallocene-catalyzed polyethylene),polypropylene, poly(4-methylpentene), and other olefinic resins, (A2)alicyclic hydrocarbon resins (e.g., hydrogenated products of ring-openedpolymers of cyclic olefins, and copolymers of cyclic olefins withethylene) each having a constitutional repeating unit represented by thefollowing formula (2):

(wherein ring A is an alicyclic hydrocarbon ring to which one or morerings may be condensed), (A3) polystyrene, styrene-acrylonitrilecopolymers, and other aromatic hydrocarbon resins (polymers eachcontaining an aromatic vinyl compound as a monomeric component), and(A4) polymers each containing, as a monomeric component, an alicyclicvinyl compound such as vinyl cyclohexane and vinyladamantane.

The ring A includes, for example, cyclopentane ring, norbornane ring,tricyclo[4.3.0.1^(2,5)]decane ring, and tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecane ring. The ring A may have a substituent. Suchsubstituents include, but are not limited to, methyl, ethyl, isopropyl,and other alkyl groups (e.g., C₁-C₄ alkyl groups); cyano group; andmethoxycarbonyl, ethoxycarbonyl, butoxycarbonyl, and other ester groups(substituted oxycarbonyl groups).

Typical examples of the alicyclic hydrocarbon resins (A2) are availableunder the trade name of “ARTON” (produced by JSR), the trade name of“ZEONEX” (produced by Nippon Zeon Co., Ltd.), the trade name of “APEL”(produced by MITSUI CHEMICALS, INC.), and the trade name of “APO”(produced by MITSUI CHEMICALS, INC.).

As the polymers constituting the molded plastics and the polymers to bemodified, (B) acrylic resins (acrylic resins each having an alicycliccarbon ring in a molecule) having a constitutional repeating unitrepresented by the following formula (3):

(wherein R is a hydrogen atom or a methyl group, and ring B is amonocyclic or polycyclic alicyclic carbon ring) are also preferred. Suchacrylic resins exhibit a higher hydrophobicity and less changes inoptical characteristics and in dimension due to moisture absorption, ascompared with, for example, poly (methyl methacrylate) . In addition,poly (methyl acrylate) and poly (methyl methacrylate) are also preferredas the polymers to be modified.

The ring B may have a substituent such as methyl, ethyl, isopropyl, andother alkyl groups (e.g., C₁-C₄ alkyl groups). Typical examples of thering B include tricyclo[5.2.1.0^(2,6)]decane ring, adamantane ring,norbornene ring, decalin ring, and perhydroanthracene ring. The acrylicresins each having an alicyclic carbon ring may be a homopolymer of a(meth) acrylic ester corresponding to the constitutional repeating unitrepresented by the formula (3) or a copolymer of the (meth)acrylic esterwith another copolymerizable monomer such as methyl methacrylate.

The polymers constituting the molded plastics and the polymer to bemodified should preferably have a secondary or tertiary carbon atom,from viewpoints of reactivity with respect to the oxygen-atom-containinggas. Among them, polymers each having a tertiary carbon atom areespecially preferred.

Molding techniques for the molded plastics are not specifically limited,and the present invention can be applied to a variety of molded plasticsobtained by conventional molding techniques such as injection molding,extrusion molding, blow molding, calendering, compression molding,transfer molding, laminate molding, and casting. The molded plastics maybe molded articles obtained by heat curing or UV curing. The shapes ofthe molded plastics are also not specifically limited and maybe any formof, for example, film, sheet, column, block, pellet, and powder, and mayexhibit a complicated shape.

According to the present invention, the imide compound represented bythe formula (1) is used as a catalyst. Of the substituents R¹ and R²inthe imide compound, the halogen atom includes iodine, bromine, chlorineand fluorine atoms. The alkyl group includes, but is not limited to,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl,hexyl, and decyl groups, and other straight- or branched-chain alkylgroups each having about 1 to 10 carbon atoms. Preferred alkyl groupsare alkyl groups each having about 1 to 6 carbon atoms, of which loweralkyl groups each having about 1 to 4 carbon atoms are especiallypreferred.

The aryl group includes phenyl and naphthyl groups, for example.Illustrative cycloalkyl groups include cyclopentyl and cyclohexylgroups. Illustrative alkoxy groups are methoxy, ethoxy, isopropoxy,butoxy, t-butoxy, andhexyloxygroups, and other alkoxy groups each havingabout 1 to 10 carbon atoms, and preferably having about 1 to 6 carbonatoms. Among them, lower alkoxy groups each having about 1 to 4 carbonatoms are especially preferred.

Examples of the alkoxycarbonyl group include methoxycarbonyl,ethoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, t-butoxycarbonyl,and hexyloxycarbonyl groups, and other alkoxycarbonyl groups each havingabout 1 to 10 carbon atoms in the alkoxy moiety. Preferred carbonylgroups are alkoxycarbonyl groups each having about 1 to 6 carbon atomsin the alkoxy moiety, of which lower alkoxycarbonyl groups each havingabout 1 to 4 carbon atoms in the alkoxy moiety are especially preferred.Illustrative acyl groups include formyl, acetyl, propionyl, butyryl,isobutyryl, valeryl, isovaleryl, and pivaloyl groups, and other acylgroups each having about 1 to 6 carbon atoms.

The substituents R¹ and R² may be identical to or different from eachother. The substituents R¹ and R²in the formula (1) may be combined witheach other to form a double bond, or an aromatic or non-aromatic ring.The preferred aromatic or non-aromatic ring has about 5 to 12 members,and particularly about 6 to 10 members. The ring may be a heterocyclicring or condensed heterocyclic ring, but it is often a hydrocarbon ring.Such rings include, for example, non-aromatic alicyclic rings (e.g.,cyclohexane ring and other cycloalkane rings which may have asubstituent; and cyclohexene ring and other cycloalkene rings which mayhave a substituent), non-aromatic bridged rings (e.g., 5-norbornene ringand other bridged hydrocarbon rings which may have a substituent),benzene ring, naphthalene ring, and other aromatic rings (includingcondensed rings) which may have a substituent. The ring is composed ofan aromatic ring in many cases. The ring may have a substituent. Suchsubstituents include, but are not limited to, alkyl groups, haloalkylgroups, hydroxyl group, alkoxy groups, carboxyl group, alkoxycarbonylgroups, acyl groups, nitro group, cyano group, amino group, and halogenatoms.

In the formula (1), X represents an oxygen atom or a hydroxyl group, andthe bond between the nitrogen atom N and X is a single bond or a doublebond.

One or two of N-substituted cyclic imido group indicated in the formula(1) may be further formed on R¹, R², or on the double bond or aromaticor non-aromatic ring formed by R¹ and R². For example, when R¹ or R² isan alkyl group having two or more carbon atoms, the N-substituted cyclicimido group may be formed together with the adjacent two carbon atomsconstituting the alkyl group. Likewise, when R¹ and R² are combined witheach other to form a double bond, the N-substituted cyclic imido groupmay be formed together with the double bond. In case that R¹ and R² arecombined with each other to form an aromatic or non-aromatic ring, theN-substituted cyclic imido group may be formed with the adjacent twocarbon atoms constituting the ring.

Preferred imide compounds include compounds of the following formulae:

(wherein R³ to R⁶ are each, identical to or different from one another,a hydrogen atom, an alkyl group, a haloalkyl group, a hydroxyl group, analkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group,a nitro group, a cyano group, an amino group, or a halogen atom, oradjacent groups of R³ to R⁶ may be combined with each other to form anaromatic or non-aromatic ring; in the formula (1f), A is a methylenegroup or an oxygen atom, and R¹, R² and X have the same meanings asdefined above, where one or two of N-substituted cyclic imido groupindicated in the formula (1c) may be further formed on a benzene ring inthe formula (1c)).

In the substituents R³ to R⁶, the alkyl group includes similar alkylgroups to those exemplified above, especially alkyl groups each havingabout 1 to 6 carbon atoms. The haloalkyl group includes trifluoromethylgroup, and other haloalkyl groups each having about 1 to 4 carbon atoms.The alkoxy group includes similar alkoxy groups to those mentionedabove, and especially lower alkoxy groups each having about 1 to 4carbon atoms. The alkoxycarbonyl group includes similar alkoxycarbonylgroups to those described above, particularly lower alkoxycarbonylgroups each having about 1 to 4 carbon atoms in the alkoxy moiety. Theacyl group includes similar acyl groups to those described above,especially acyl groups each having about 1 to 6 carbon atoms.Illustrative halogen atoms include fluorine, chlorine and bromine atoms.Each of the substituents R³ to R⁶ is usually a hydrogen atom, a loweralkyl group having about 1 to 4 carbon atoms, a carboxyl group, a nitrogroup, or a halogen atom in many cases. The ring formed by R³ to R⁶includes similar rings to the aforementioned rings which are formed byR¹ and R². Among them, aromatic or non-aromatic 5- to 12-membered ringsare particularly preferred.

Typically preferred imide compounds include, for example,N-hydroxysuccinimide, N-hydroxymaleimide, N-hydroxyhexahydrophthalimide,N,N′-dihydroxycyclohexanetetracarboximide, N-hydroxyphthalimide,N-hydroxytetrabromophthalimide, N-hydroxytetrachlorophthalimide,N-hydroxychlorendimide, N-hydroxyhimimide, N-hydroxytrimellitimide,N,N′-dihydroxypyromellitimide, andN,N′-dihydroxynaphthalenetetracarboximide.

The imide compounds can be prepared by a conventional imidation reaction(a reaction for the formation of an imide), such as a process thatcomprises the steps of allowing a corresponding acid anhydride to reactwith hydroxylamine NH₂OH for ring-opening of an acid anhydride group,and closing the ring to form an imide.

Such acid anhydrides include, but are not limited to, succinicanhydride, maleic anhydride, and other saturated or unsaturatedaliphatic dicarboxylic anhydrides, tetrahydrophthalic anhydride,hexahydrophthalic anhydride (1,2-cyclohexanedicarboxylic anhydride),1,2,3,4-cyclohexanetetracarboxylic 1,2-dianhydride, and other saturatedor unsaturated non-aromatic cyclic polycarboxylic anhydrides (alicyclicpolycarboxylic anhydrides), HET anhydride (chlorendic anhydride), himicanhydride, and other bridged cyclic polycarboxylic anhydrides (alicyclicpolycarboxylic anhydrides), phthalic anhydride, tetrabromophthalicanhydride, tetrachlorophthalic anhydride, nitrophthalic anhydride,trimellitic anhydride, methylcyclohexenetricarboxylic anhydride,pyromellitic anhydride, mellitic anhydride,1,8;4,5-naphthalenetetracarboxylic dianhydride, and other aromaticpolycarboxylic anhydrides.

Typically preferred imide compounds include N-hydroxyimide compoundsderived from alicyclic polycarboxylic anhydrides or aromaticpolycarboxylic anhydrides, of which N-hydroxyphthalimide and otherN-hydroxyimide compounds derived from aromatic polycarboxylic anhydridesare especially preferred. Each of the imide compounds represented by theformula (1) can be used alone or in combination.

In the invented method, the amount of the imide compound represented bythe formula (1) for use as a catalyst can be selected within a widerange, and is for example such that the concentration in a treatingsolution for use in the treatment of the molded plastic or the polymeris about 0.001 to 1 mol/l, and preferably about 0.01 to 0.5 mol/l.

According to the present invention, a promoter (co-catalyst) can be usedin addition to the imide compound. Such promoters include metalliccompounds. The use of a metallic compound as the promoter can improvethe rate and selectivity of a reaction.

Metallic elements constituting the metallic compounds are not critical,but elements of Groups 2 to 15 of the Periodic Table of Elements areused in many cases. The term “metallic element” as used in the presentdescription also includes boron B. Examples of the metallic elementsinclude, of the Periodic Table of Elements, Group 2 elements (e.g., Mg,Ca, Sr, and Ba), Groups 3 elements (e.g., Sc, lanthanoid elements, andactinoid elements), Group 4 elements (e.g., Ti, Zr, and Hf), Group 5elements (e.g., V), Group 6 elements (e.g., Cr, Mo, and W), Group 7elements (e.g., Mn), Group 8 elements (e.g., Fe and Ru), Group9elements(e.g., Co and Rh), Group 10 elements (e.g., Ni, Pd, and Pt), Group 11elements (e.g., Cu), Group 12 elements (e.g., Zn), Groups 13 elements(e.g., B, Al, and In), Group 14 elements (e.g., Sn and Pb), and Group 15elements (e.g., Sb and Bi). Preferred metallic elements includetransition metal elements (elements of Groups 3 to 12 of the PeriodicTable of Elements). Among them, elements of the Groups 5 to 11,especially elements of Groups 5 to 9 of the Periodic Table of Elementsare preferred, of which V, Mo, Mn, and Co are typically preferred. Thevalence of the metallic element is not critical, and is, for example,about 0 to 6.

The metallic compounds include, but are not limited to, elementarysubstances, hydroxides, oxides (including complex oxides), halides(fluorides, chlorides, bromides, and iodides), salts of oxoacids (e.g.,nitrates, sulfates, phosphates, borates, and carbonates), salts ofisopolyacids, salts of heteropolyacids, and other inorganic compounds ofthe aforementioned metallic elements; salts of organic acids (e.g.,acetates, propionates, hydrocyanates, naphthenates, and stearates),complexes, and other organic compounds of the metallic elements. Ligandsconstituting the complexes include OH (hydroxo), alkoxy (e.g., methoxy,ethoxy, propoxy, and butoxy), acyl (e.g., acetyl and propionyl),alkoxycarbonyl (e.g., methoxycarbonyl and ethoxycarbonyl),acetylacetonato, cyclopentadienyl group, halogen atoms (e.g., chlorineand bromine), CO, CN, oxygen atom, H₂O (aquo), phosphines (e.g.,triphenylphosphine and other triarylphosphines) and other phosphoruscompounds, NH₃ (ammine), NO, NO₂ (nitro), NO₃ (nitrato),ethylenediamine, diethylenetriamine, pyridine, phenanthroline, and othernitrogen-containing compounds.

Examples of the metallic compounds include, by taking cobalt compoundsas example, cobalt hydroxide, cobalt oxide, cobalt chloride, cobaltbromide, cobalt nitrate, cobalt sulfate, cobalt phosphate, and otherinorganic compounds; cobalt acetate, cobalt naphthenate, cobaltstearate, and other salts of organic acids; acetylacetonatocobalt andother complexes, and other divalent or trivalent cobalt compounds.Illustrative vanadium compounds include vanadium hydroxide, vanadiumoxide, vanadium chloride, vanadyl chloride, vanadium sulfate, vanadylsulfate, sodiumvanadate, andotherinorganic compounds;acetylacetonatovanadium, vanadyl acetylacetonato, and other complexes,and other vanadium compounds having a valence of 2 to 5. Examples ofcompounds of the other metallic elements include compounds correspondingto the above-mentioned cobalt or vanadium compounds. Each of thesemetallic compounds can be used alone or in combination.

The amount of the metallic compound is, for example, about 0.001 to 0.1mole, and preferably about 0.005 to 0.08 mole, relative to 1 mole of theimide compound.

As the promoters for use in the present invention, organic salts eachcomposed of a polyatomic cation or a polyatomic anion and its counterion can also be used, which polyatomic cation or anion contains a Group15 or Group 16 element of the Periodic Table of Elements having at leastone organic group combined therewith. The use of the organic salt as thepromoter can further enhance or improve the rate and selectivity of thereaction.

In the organic salts, the Group 15 elements of the Periodic Table ofElements include N, P, As, Sb, and Bi, and the Group 16 elements of thePeriodic Table of Elements include, for example, O, S, Se and Te.Preferred elements are N, P, As, Sb, and S, of which N, P, and S aretypically preferred.

The organic groups to be combined with atoms of the elements include,but are not limited to, hydrocarbon groups which may have a substituent,and substituted oxy groups. Such hydrocarbon groups include, but are notlimited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl,t-butyl, pentyl, hexyl, octyl, decyl, tetradecyl, hexadecyl, octadecyl,allyl, and other straight- or branched-chain aliphatic hydrocarbongroups (alkyl groups, alkenyl groups, and alkynyl groups) each havingabout 1 to 30 carbon atoms (preferably about 1 to 20 carbon atoms);cyclopentyl, cyclohexyl, and other alicyclic hydrocarbon groups eachhaving about 3 to 8 carbon atoms; and phenyl, naphthyl, and otheraromatic hydrocarbon groups each having about 6 to 14 carbon atoms.Substituents which the hydrocarbon groups may have include, but are notlimited to, halogen atoms, oxo group, hydroxyl group, substituted oxygroups (e.g., alkoxy groups, aryloxy groups, and acyloxy groups),carboxyl group, substituted oxycarbonyl groups, substituted orunsubstituted carbamoyl groups, cyano group, nitro group, substituted orunsubstituted amino groups, alkyl groups (e.g., methyl, ethyl, and otherC₁-C₄ alkyl groups), cycloalkyl groups, aryl groups (e.g., phenyl andnaphthyl groups), and heterocyclic groups. Preferred hydrocarbon groupsinclude, for example, alkyl groups each having about 1 to 30 carbonatoms, and aromatic hydrocarbon groups (especially, phenyl group ornaphthyl group) each having about 6 to 14 carbon atoms. The substitutedoxy groups include, but are not limited to, alkoxy groups, aryloxygroups and aralkyloxy groups.

Typical examples of the organic salts include organic onium salts suchas organic ammonium salts, organic phosphonium salts, and organicsulfonium salts. Examples of organic ammonium salts includetetramethylammonium chloride, tetraethylammonium chloride,tetrabutylammonium chloride, tetrahexylammonium chloride,trioctylmethylammonium chloride, triethylphenylammonium chloride,tributyl(hexadecyl)ammonium chloride, di (octadecyl) dimethylammoniumchloride, and other quaternary ammonium chlorides, correspondingquaternary ammonium bromides, and other quaternary ammonium salts eachhaving four hydrocarbon groups combined with a nitrogen atom;dimethylpiperidinium chloride, hexadecylpyridinium chloride,methylquinolinium chloride, and other cyclic quaternary ammonium salts.Examples of the organic phosphonium salts include tetramethylphosphoniumchloride, tetrabutylphosphonium chloride, tributyl(hexadecyl)phosphonium chloride, triethylphenylphosphonium chloride, andother quaternary phosphonium chlorides, corresponding quaternaryphosphonium bromides, and other quaternary phosphonium salts each havingfour hydrocarbon groups combined with a phosphorus atom. Examples of theorganic sulfonium salts include triethylsulfonium iodide,ethyldiphenylsulfonium iodide, and other sulfonium salts each havingthree hydrocarbon groups combined with a sulfur atom.

The organic salts also include methanesulfonates, ethanesulfonates,octanesulfonates, dodecanesulfonates, and other alkyl-sulfonates (e.g.,C₆-C₁₈ alkyl-sulfonates); benzenesulfonates, p-toluenesulfonates,naphthalenesulfonates, decylbenzenesulfonates, dodecylbenzenesulfonates,and other aryl-sulfonates which may be substituted with an alkyl group(e.g., C₆-C₁₈ alkyl-substituted aryl-sulfonates); sulfonic acid type ionexchange resins (ion exchangers); and phosphonic acid type ion exchangeresins (ion exchangers).

The amount of the organic salt is, for example, about 0.001 to 0.1 mole,and preferably about 0.005 to 0.08 mole, relative to 1 mole of the imidecompound.

In the present invention, a strong acid can be used in combination withthe imide compound. The combination use of the imide compound and thestrong acid can efficiently introduce an oxo group into a methylenecarbon atom (secondary carbon atom) of the polymer constituting themolded plastic or the polymer to be modified, with the use of oxygen asthe oxygen-atom-containing gas.

The strong acids include, for example, compounds each having a pKa of 2or less (25° C.). The pKa of the strong acid is preferably about −15 to2, and more preferably about −10 to 0. Such strong acids include, butare not limited to, hydrogen halides (hydrogen fluoride, hydrogenchloride, hydrogen bromide, and hydrogen iodide), hydrohalogenic acids(hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydroiodicacid), oxoacids (e.g., sulfuric acid, nitric acid, phosphoric acid,chromic acid and other metallic acids, chloric acid, and other halogenacids), super strong acids (e.g., ClSO₃H, H₂SO₄—SO₃, FSO₃H, FSO₃H—SO₃,FSO₃H—SbF₅, and HF—SbF₅), heteropolyacids (e.g., silicomolybdic acid,silicotungstic acid, phosphomolybdic acid, phosphotungstic acid,phosphovanadomolybdic acid, and phosphovanadotungstic acid), andsulfonic acids (e.g., methanesulfonic acid, trifluoromethanesulfonicacid, benzenesulfonic acid, p-toluenesulfonic acid, an dnaphthalenesulfonic acid). Preferred strong acids include inorganicacids such as hydrogen halides, hydrohalogenic acids , sulfuric acid,and heteropolyacids. Each of these strong acids can be used alone or incombination. The amount of the strong acid is, for example, about 0.001to 3 moles, and preferably about 0.1 to 1 mole, relative to 1 mole ofthe imide compound

According to the invented method, a reaction system may include aradical generator or a radical reaction accelerator. Such componentsinclude, but are not limited to, halogens (e. g., chlorine and bromine),peracids (e.g., peracetic acid and m-chloroperbenzoic acid), andperoxides (e.g., hydrogen peroxide, t-butyl hydroperoxide (TBHP), andother hydroperoxides). The existence of these components in the systemcan accelerate a reaction in some cases. The amount of theaforementioned component is, for example, about 0.001 to 0.1 molerelative to 1 mole of the imide compound.

In the present invention, a co-reacting agent (co-reactant; a compoundwhich can react with an oxygen-atom-containing gas in the presence ofthe imide compound; refer to, for example, Japanese Unexamined PatentApplication Publication No. 8-38909, and Japanese Unexamined PatentApplication Publication No. 9-327626) can coexist in the reactionsystem. The coexistence of the co-reacting agent in the reaction systemcan accelerate the reaction and the surface of molded plastic or thepolymer can be hydrophilized in a short time in many cases. This isprobably because the co-reacting agent plays a role as a radicalgenerator.

As such co-reacting agents, use may be made of, for example, at leastone compound selected from (a) primary or secondary alcohols, (b)compounds each having a carbon-hydrogen bond at the adjacent position toan unsaturated bond, (c) compounds each having a methine carbon atom,(d) cycloalkanes, (e) non-aromatic heterocyclic compounds each having acarbon-hydrogen bond at the adjacent position to a hetero atom, (f)conjugated compounds, (g) aromatic hydrocarbons, (h) thiols, (i) ethers,(j) sulfides, (k) aldehydes or thioaldehydes, and (l) amines. Thesecompounds may have a variety of substituents. Such substituents include,but are not limited to, halogen atoms, oxo group, hydroxyl group,mercapto group, substituted oxy groups (e.g., alkoxy groups, aryloxygroups, and acyloxy groups), substituted thio groups, carboxyl group,substituted oxycarbonyl groups, substituted or unsubstituted carbamoylgroups, cyano group, nitro group, substituted or unsubstituted aminogroups, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups,cycloalkenyl groups, aryl groups (e.g., phenyl and naphthyl groups),aralkyl groups, and heterocyclic groups.

(a) Primary or Secondary Alcohols

The primary or secondary alcohols (a) include a wide variety ofalcohols. These alcohols may be any of monohydric, dihydric orpolyhydric alcohols. Such primary alcohols include, but are not limitedto, methanol, ethanol, 1-propanol, 1-butanol, 1-decanol, ethyleneglycol, and other saturated or unsaturated aliphatic primary alcohols;cyclopentylmethyl alcohol, cyclohexylmethyl alcohol, and other saturatedor unsaturated alicyclic primary alcohols; benzyl alcohol, 2-phenylethylalcohol, and other aromatic primary alcohols; and2-hydroxymethylpyridine, and other heterocyclic alcohols. Illustrativesecondary alcohols include 2-propanol, s-butyl alcohol, and othersaturated or unsaturated aliphatic secondary alcohols; cyclopentanol,cyclohexanol, and other saturated or unsaturated alicyclic secondaryalcohols; 1-phenylethanol, 1-phenylpropanol, 1-phenylmethylethanol,diphenylmethanol, and other aromatic secondary alcohols; and1-(2-pyridyl)ethanol, and other heterocyclic secondary alcohols.Preferred primary or secondary alcohols (a) include secondary alcohols(e.g., s-butyl alcohol and other aliphatic secondary alcohols,cyclohexanol and other alicyclic secondary alcohols, 1-phenylethanol andother aromatic secondary alcohols). Each of the alcohols (a) can be usedalone or in combination.

(b) Compounds Each Having a Carbon-hydrogen Bond at the AdjacentPosition to an Unsaturated Bond

The compounds (b) each having a carbon-hydrogen bond at the adjacentposition to an unsaturated bond include, for example, (b1) aromaticcompounds each having a methyl group or methylene group at the adjacentposition to an aromatic ring (so-called benzyl position), and (b2)non-aromatic compounds each having a methyl group or methylene group atthe adjacent position to an unsaturated bond (e.g., a carbon-carbontriple bond or a carbon-oxygen double bond). In the aromatic compounds(b1), the aromatic ring may be either of an aromatic hydrocarbon ring oran aromatic heterocyclic ring. The methylene group at the adjacentposition to an aromatic ring may be a methylene group constituting anon-aromatic ring condensed to the aromatic ring. Such aromaticcompounds each having a methyl group at the adjacent position to anaromatic ring include aromatic hydrocarbons having one to six methylgroups substituted on the aromatic ring (e.g., toluene, xylene, andmethylnaphthalene), and heterocyclic compounds each having about one tosix methyl groups substituted on a heterocyclic ring (e.g.,4-methylpyridine). Illustrative aromatic compounds each having amethylene group at the adjacent position to an aromatic ring include,but are not limited to, aromatic hydrocarbons each having an alkyl groupor substituted alkyl group having 2 or more carbon atoms (e.g.,ethylbenzene, propylbenzene, and diphenylmethane), aromatic heterocycliccompounds each having an alkyl group or substituted alkyl group having 2or more carbon atoms (e.g., 4-ethylpyridine), and compounds in which anon-aromatic ring is condensed to an aromatic ring, and the non-aromaticring has a methylene group at the adjacent position to the aromatic ring(e.g., dihydronaphthalene, indene, indan, tetralin, fluorene,acenaphthene, phenalene, and xanthene).

The non-aromatic compounds (b2) each having a methyl group or methylenegroup at the adjacent position to an unsaturated bond include, but arenot limited to, (b2-1) unsaturated chain hydrocarbons each having amethyl group or methylene group at the adjacent position to acarbon-carbon triple bond, and (b2-2) compounds each having a methylgroup or methylene group at the adjacent position to a carbonyl group.The unsaturated chain hydrocarbons (b2-1) include, for example,methylacetylene, and other alkynes each having about 3 to 20 carbonatoms. The compounds (b2-2) include, but are not limited to, ketones(e.g., acetone, methyl ethyl ketone, 3-pentanone, acetophenone, andother chain ketones; and cyclohexanone and other cyclic ketones), andcarboxylic acids or derivatives thereof (e.g., malonic acid, succinicacid, glutaric acid, and esters of these acids).

(c) Compounds Each Having a Methine Carbon Atom

The compounds (c) each having a methine carbon atom (or a tertiarycarbon atom) include (c1) cyclic compounds each having a methine group(i.e., a methine carbon-hydrogen bond) as a constitutive unit of a ring,and (c2) chain compounds each having a methine carbon atom. The cycliccompounds (c1) include, for example, (c1-1) bridged cyclic compoundseach having at least one methine group, and (c1-2) non-aromatic cycliccompounds (e.g., alicyclic hydrocarbons) each having a hydrocarbon groupcombined with a ring. The bridged cyclic compounds also includecompounds in which two rings commonly possess two carbon atoms, such ashydrogenated products of condensed polycyclic aromatic hydrocarbons.

Illustrative bridged cyclic compounds (c1-1) include decalin,bicyclo[2.2.2]octane, pinane, pinene, bornane, norbornane, norbornene,camphor, endotricyclo[5.2.1.0^(2,6)] decane, adamantane, 1-adamantanol,perhydroanthracene, and other bridged cyclic hydrocarbons or bridgedheterocyclic compounds each having two to four rings, and derivativesthereof. These bridged cyclic compounds each have a methine carbon atomat the bridgehead position (corresponding to a junction position whentwo rings commonly possess two atoms). Examples of the non-aromaticcyclic compounds (c1-2) each having a hydrocarbon group combined with aring include 1-methylcyclopentane, 1-methylcyclohexane, and otheralicyclic hydrocarbons each having a hydrocarbon group (e.g., an alkylgroup) combined with a ring, and derivatives thereof. The non-aromaticcyclic compounds (c1-2) each having a hydrocarbon group combined withring have a methine carbon atom at the bonding site between the ring andthe hydrocarbon group.

Chain compounds (c2) each having a methine carbon atom include chainhydrocarbons each having a tertiary carbon atom, such as isobutane,isopentane, isohexane, 3-methylpentane, and other aliphatichydrocarbons, and derivatives thereof.

(d) Cycloalkanes

The cycloalkanes (d) include, but are not limited to, cyclopentane,cyclohexane, cycloheptane, cyclooctane, cyclododecane, cyclotetradecane,and derivatives of these compounds.

(e) Non-aromatic heterocyclic compounds each having a carbon-hydrogenbond at the adjacent position to a hetero atom In the non-aromaticheterocyclic compounds (e) each having a carbon-hydrogen bond at theadjacent position to a hetero atom, non-aromatic heterocyclic ringsinclude, but are not limited to, heterocyclic rings each having at leastone hetero atom selected from nitrogen atom, oxygen atom and sulfuratom. To each of the heterocyclic rings, one or two of benzene rings,cyclohexane rings, pyridine rings or other aromatic or non-aromaticrings may be condensed. The heterocyclic rings include, for example,dihydrofuran, tetrahydrofuran, pyran, dihydropyran, tetrahydropyran,pyrrolidine, piperidine, piperazine, morpholine, indoline, chroman, andisochroman.

(f) Conjugated Compounds

The conjugated compounds (f) include, for example, (f1) conjugateddienes, (f2) α,β-unsaturated nitriles, and (f3) α,β-unsaturatedcarboxylic acids or derivatives thereof (e.g., esters, amides andanhydrides). The conjugated dienes (f1) include, but are not limited to,butadiene, and isoprene. The conjugated dienes (f1) also include vinylacetylene and other compounds in which a double bond and a triple bondare conjugated. The α,β-unsaturated nitriles (f2) include, for example,(meth)acrylonitrile. The α,β-unsaturated carboxylic acids or derivativesthereof (f3) include, but are not limited to, (meth)acrylic acid; methyl(meth)acrylate, ethyl (meth)acrylate, and other (meth)acrylic esters;and (meth)acrylamide or derivatives thereof.

(g) Aromatic Hydrocarbons

The aromatic hydrocarbons (g) include, but are not limited to, benzene,naphthalene, acenaphthylene, phenanthrene, anthracene, naphthacene, andother aromatic compounds each having at least one benzene ring. Of thesecompounds, preferred are condensed polycyclic aromatic compounds inwhich at least plural benzene rings (e.g., two to ten benzene rings) arecondensed. These aromatic hydrocarbons may each have one or moresubstituents. Examples of such aromatic compounds each having asubstituent include 2-chloronaphthalene, 2-methoxynaphthalene,1-methylnaphthalene, 2-methylnaphthalene, 2-methylanthracene,2-t-butylanthracene, 2-carboxyanthracene, 2-ethoxycarbonylanthracene,2-cyanoanthracene, 2-nitroanthracene, and 2-methylpentalene. To thebenzene ring, a non-aromatic carbon ring, an aromatic heterocyclic ring,or a non-aromatic heterocyclic ring may be condensed.

(h) Thiols

The thiols (h) include, but are not limited to, methanethiol,ethanethiol, and other aliphatic thiols; cyclopentanethiol, and otheralicyclic thiols; and phenylmethanethiol, and other aromatic thiols.

(i) Ethers

Examples of the ethers (i) include diethyl ether, dipropyl ether, andother aliphatic ethers; and anisole, dibenzyl ether, and other aromaticethers.

(j) Sulfides

The sulfides (j) include, but are not limited to, diethyl sulfide,dipropyl sulfide, and other aliphatic sulfides; and methyl phenylsulfide, ethyl phenyl sulfide, and other aromatic sulfides.

(k) Aldehydes or Thioaldehydes

The aldehydes include, but are not limited to, acetaldehyde,propionaldehyde, hexanal, decanal, succinaldehyde, glutaraldehyde,adipaldehyde, and other aliphatic aldehydes; formylcyclohexane, andother alicyclic aldehydes; benzaldehyde, nitrobenzaldehyde,cinnamaldehyde, salicylaldehyde, anisaldehyde, phthalaldehyde,isophthalaldehyde, terephthalaldehyde, and other aromatic aldehydes; andfurfural, nicotinic aldehyde, and other heterocyclic aldehydes. Thethioaldehydes include thioaldehydes corresponding to the aforementionedaldehydes.

(l) Amines

The illustrative amines (l) are primary or secondary amines such asmethylamine, ethylamine, propylamine, butylamine, dimethylamine,diethylamine, ethylenediamine, hydroxylamine, ethanolamine, and otheraliphatic amines; cyclohexylamine, and other alicyclic amines;benzylamine, toluidine, and other aromatic amines.

Of these co-reacting agents, preferred compounds are the (a) primary orsecondary alcohols, (b) compounds each having a carbon-hydrogen bond atthe adjacent position to an unsaturated bond, (c) compounds each havinga methine carbon atom, and (d) cycloalkanes. Among them, typicallypreferred are secondary alcohols, (b1) aromatic compounds each having amethyl group or methylene group at the adjacent position to an aromaticring (a so-called benzyl position), and adamantane and other bridgedcyclic compounds each having a methine carbon atom. Such preferredcompounds (b1) include, but are not limited to, toluene, ethylbenzene,and other aromatic hydrocarbons each having a methyl group or methylenegroup at the adjacent position to an aromatic ring; and fluorene,tetralin, and other compounds each having a non-aromatic ring condensedto an aromatic ring, and having a methylene group at a position in thenon-aromatic ring adjacent to the aromatic ring.

Each of the co-reacting agents can be used alone or in combination. Theamount of the co-reacting agent can be selected within a wide range, andis for example such that the concentration in a treating solution foruse in the treatment of the molded plastic or the polymer is about 0.001to 10 mol/l, preferably about 0.01 to 5 mol/l, and specifically about0.1 to 3mol/l. Theco-reactingagentcanalsobeusedasareaction solvent.

In the present invention, the system may further comprise a1,2-dicarbonyl compound or its hydroxy reductant. When the 1,2-dicarbonyl compound or its hydroxy reductant exits in the system andoxygen is used as the oxygen-containing gas, an acyl group is introducedinto a carbon atom (especially, a methine carbon atom) constituting thepolymer molecule of the molded plastic or the molecule of the polymer tobe modified, and thereby the surface of the molded plastic or thepolymer is hydrophilized.

The 1,2-dicarbonyl compound or its hydroxy reductant includes a compoundrepresented by the following formula (4):

(wherein R^(a) and R^(b) are each, identical to or different from eachother, a hydrogen atom, a hydrocarbon group, or a heterocyclic group, orR^(a) and R^(b) may be combined with each other to form a ring withadjacent two carbon atoms; and Z¹ and Z² are each, identical to ordifferent from each other, an oxygen atom or a hydroxyl group).

Hydrocarbon groups in R^(a) and R^(b) include, but are not limited to,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl,pentyl, hexyl, octyl, decyl, tetradecyl, hexadecyl, octadecyl, allyl,and other straight- or branched chain aliphatic hydrocarbon groups(alkyl groups, alkenyl group, and alkynyl groups) each having about 1 to20 (preferably 1 to 10, andparticularlyl to 6) carbonatoms; cyclopentyl,cyclohexyl, and other alicyclic hydrocarbon groups (cycloalkyl groupsand cycloalkenyl groups) each having about 3 to 8 carbon atoms; phenyl,naphthyl, and other aromatic hydrocarbon groups (aryl groups) eachhaving about 6 to 14 carbon atoms.

Heterocylces in the heterocyclic group include, but are not limited to,tetrahydrofuran, pyrrolidine, piperidine, piperazine, morpholine,indoline, furan, oxazole, thiophene, pyrrole, pyrazole, imidazole,pyridine, pyridazine, pyrimidine, pyrazine, indole, quinoline, and otherheterocyclic rings (including condensed rings) containing about one tothree of at least one hetero atom selected from nitrogen atom, oxygenatom, and sulfur atom, and having about 3 to 15 members (preferablyabout 5 to 12 members, and more preferably about 5 or 6 members).

The hydrocarbon groups and heterocyclic groups may have a variety ofsubstituents. Such substituents include, for example, halogenatoms,oxogroup, hydroxylgroup, substituted oxy groups (e.g., alkoxy groups,aryloxy groups, and acyloxy groups), carboxyl group, substitutedoxycarbonyl groups, substituted or unsubstituted carbamoyl groups, cyanogroup, nitro group, substituted or unsubstituted amino groups, alkylgroups, cycloalkyl groups, aryl groups (e.g., phenyl and naphthylgroups), and heterocyclic groups. In many cases, R^(a) and R^(b) areidentical groups.

R^(a) and R^(b) may be combined to form a ring with the adjacent twocarbon atoms. Such rings include, for example, cyclopentane ring,cyclohexane ring, and other cycloalkane rings each having about 3 to 15members (preferably 5 or 6 members). The rings may have suchsubstituents as mentioned above.

Each of Z¹ and Z² is an oxygen atom or a hydroxyl group, and a bondbetween the carbon atom and Z¹ or Z² is a single bond or a double bond.

Of the compounds represented by the formula (4), preferred compoundsinclude a compound represented by the following formula (4a):

(wherein R^(a1) and R^(b1) are each, identical to or different from eachother, an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group, oran aryl group, or R^(a1) and R^(b1) may be combined to form a ring withadjacent two carbon atoms; and Z¹ and Z² are each, identical to ordifferent from each other, an oxygen atom or a hydroxyl group).

Typically preferred R^(a1) and R^(b1) are methyl group or ethyl group,of which methyl group is especially preferred. R^(a1) and R^(b1) areidentical groups in many cases.

Preferred examples of the 1,2-dicarbonyl compounds include biacetyl(2,3-butanedione), 2,3-pentanedione, 3,4-hexanedione, bibenzoyl(benzil), acetylbenzoyl, cyclopentane-1,2-dione, cyclohexane-1,2-dione,and other α-diketones. Among them, biacetyl or the like is preferred.Preferred examples of the hydroxy reductant of the 1,2-dicarbonylcompound include acetoin, benzoin, and other α-keto-alcohols;2,3-butanediol, 2,3-pentanediol, and other vicinal diols. Among them,acetoin and 2,3-butanediol are preferred, for example.

The amount of the 1,2-dicarbonyl compound or its hydroxy reductant is,for example, about 2 to 1000 moles, and preferably about 5 to 500 moles,relative to 1 mole of the imide compound. When the 1,2-dicarbonylcompound or its hydroxy reductant is used, the metallic compound may beused instead of, or in addition to the imide compound.

The oxygen-atom-containing gas (hereinafter referred to as “reactiongas”) for use in the present invention include, for example, oxygen,carbon monoxide, nitrogen oxides, and sulfur oxides. Each of these gasescan be used alone or in combination.

The oxygen may be either molecular oxygen or active oxygen. Themolecular oxygen includes, but is not limited to, pure oxygen, andoxygen diluted with an inert gas such as nitrogen, helium, argon orcarbon dioxide, as well as air. Molecular oxygen is often used as theoxygen.

The nitrogen oxides include, but are not limited to, N₂O₃, N₂O, NO, andNO₂. These substances (e.g., N₂O, NO, or NO₂) can be used in combinationwith oxygen. The sulfuroxides include, for example, SO₂ and SO₃. Thesesubstances (e.g., SO₂) can be used in combination with oxygen.

When oxygen is used as the reaction gas, a hydroxyl group, an oxo group,or a carboxyl group is introduced into a primary carbon atom (e.g., amethyl carbon atom at benzyl position or allyl position), into asecondary carbon atom (e.g., a methylene carbon atom at benzyl positionor allyl position, or a methylene carbon atom constituting anon-aromatic carbon ring), or into a tertiary carbon atom (e.g., amethine carbon atom in a branched alkyl group or alkylene group, or amethine carbon atom at junction position or bridgehead position of apolycyclic group), of the polymer molecule on the surface of the moldedplastic or the molecule of the polymer to be modified.

The use of carbon monoxide and oxygen as the reaction gases canintroduce a carboxyl group into a carbon atom constituting polymermolecules on the surface of the molded plastic or constituting moleculesof the polymer to be modified. The ratio of carbon monoxide to oxygen issuch that carbon monoxide/oxygen (by mole) is about 1/99 to 99/1, andpreferably about 10/90 to 99/1.

When oxygen is used as the reaction gas and the 1,2-dicarbonyl compoundor its hydroxy reductant exits in the reaction system, an acyl group [anR^(a)C(═O)— or R^(b)C(═O)— when the compound represented by the formula(4) is used] is introduced into a carbon atom (particularly, a methinecarbon atom) constituting the polymer molecule on the surface of themolded plastic or constituting the molecule of the polymer to bemodified, as described above.

When the nitrogen oxide (or nitrogen oxide with oxygen) is used as thereaction gas, a nitro group is introduced into a carbon atomconstituting the polymer molecule on the surface of the molded plasticor constituting the molecule of the polymer to be modified. When thesulfur oxide (or sulfur oxide with oxygen) is used as the reaction gas,SO₃H group, SO₂H group or the like is introduced into a carbon atomconstituting the polymer molecule on the surface of the molded plasticor constituting the molecule of the polymer to be modified.

The amount of the reaction gas can be appropriately selected inconsideration of, for example, a reaction rate, a desired amount ofhydrophilic group to be introduced, and operability.

The molded plastic is generally treated by immersing the molded articlein a solvent containing the imide compound and introducing the reactiongas into the solvent. The polymer is generally treated by dissolving thepolymer in a solvent in which the polymer can be dissolved and whichcontains the imide compound, and introducing the reaction gas into thesolution. The reaction gas can also be liquified before introduction.

The solvent can be appropriately selected depending on the type of apolymer constituting the molded plastic or of the polymer to bemodified. Such solvents include, but are not limited to, acetic acid,propionic acid, and other organic acids; acetonitrile, propionitrile,benzonitrile, and other nitriles; formamide, acetamide,dimethylformamide (DMF), dimethylacetamide, and other amides; t-butanol,t-amyl alcohol, and other alcohols; hexane, octane, and other aliphatichydrocarbons; benzene, and other aromatic hydrocarbons; chloroform,dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene,dichlorobenzene, trifluoromethylbenzene, and other halogenatedhydrocarbons; nitrobenzene, nitromethane, nitroethane, and other nitrocompounds; ethyl acetate, butyl acetate, and other esters; diethylether, diisopropyl ether, and other ethers; and mixtures of thesesolvents. An appropriate amount of water may be added to the solvent. Inmany cases, acetic acid and other organic acids, benzonitrile and othernitriles, chlorobenzene, trifluoromethylbenzene, and other halogenatedhydrocarbons are used as the solvents.

When the surface of the molded plastic is to be modified, the solventshould be preferably one which has an affinity for a polymerconstituting the molded plastic but does not dissolve the polymer, inorder to keep the surface shape of the molded plastic from changing.

A treating temperature (reaction temperature) can be appropriatelyselected depending on, for example, the type of a polymer constitutingthe molded plastic or of the polymer to be modified, and the type of thereaction gas. For example, when oxygen is used as the reaction gas tothereby introduce a hydroxyl group or an oxo group into a carbon atom ofthe molded article polymer or of the polymer to be modified, thetreating temperature is about 0° C. to 300° C., and preferably about 30°C. to 250° C. (e.g., about 40° C. to 150° C.). When carbon monoxide andoxygen are used as the reaction gases to thereby introduce a carboxylgroup into a carbon atom of the molded article polymer or of the polymerto be modified, the treating temperature is, for example, about 0° C. to200° C., and preferably about 10° C. to 150° C. When the nitrogen oxideor sulfur oxide is used as the reaction gas, the treating temperatureis, for example, about 0° C. to 150° C., and preferably about 10° C. to125° C. The treatment can be performed at atmospheric pressure or undera pressure (under a load). When the treatment is performed under apressure, the pressure is usually about 1 to 100 atm (0.1 to 10 MPa)[e.g., about 1.5 to 80 atm (0.15 to 8.1 MPa)], and preferably about 2 to70 atm (0.2 to 7.1 MPa). A treating time can be appropriately selectedwithin a range of, for example, about 30 minutes to 48 hours, dependingon the treating temperature and treating pressure.

The degree of hydrophilicity of the molded plastic surface or the amountof polar group to be introduced into the polymer to be modified(introduction rate of functional group) can be controlled by adjustingthe concentration of the reaction gas, treating temperature, treatingtime, and other reaction conditions. The treatment can be performed by aconventional technique such as batch system, semi-batch system, orcontinuous system in the presence of, or under flow of the reaction gas.

The above treatment can introduce a hydroxyl group and other hydrophilicgroups into a carbon atom constituting the surface polymer of the moldedplastic to thereby impart hydrophilicity to the surface of the moldedplastic. The resulting surface-modified molded plastic is useful asoptical lenses, optical disks, and other optical materials.

When the polymer is modified, the modified polymer can be separated bysubjecting a reaction mixture to a conventional separation andpurification procedure such as reprecipitation, crystallization,recrystallization, and filtration, after the treatment of the polymerwith the reaction gas. The above-prepared modified polymer has ahydroxyl group or another polar group introduced into a carbon atomconstituting the polymer and therefore has, for example, a higherantistatic property than the original polymer.

According to the invented method for the surface modification of amolded plastic, a hydroxyl group or another hydrophilic group can beintroduced only to a carbon atom constituting a surface polymer of themolded plastic, by action of the oxygen-atom-containing gas and bycatalysis of the imide compound having a specific structure.Consequently, the hydrophobicity of inside polymers which occupy themajority of the molded plastic can be kept as intact, and thehygroscopicity of the overall molded article does not significantlychange as compared with that before the surface modification. Changes inrefractive index or in dimension due to moisture absorption cantherefore be minimized. In contrast, the surface of the molded plastichas an improved hydrophilicity to thereby increase adhesion and adhesiveproperty to a variety of coating agents (coating films), and he surfaceof the molded article shows promise for antistatic property. Theinvented method can be applied to a wide variety of molded polymers eachhaving a primary, secondary, or tertiary carbon atom, and is veryexcellent in general versatility, as the shape of the molded article isnot critical as far as a treating solution can come in contact with thesurface thereof. In addition, the degree of hydrophilicity of the moldedarticle surface can be controlled by adjusting reaction conditions(e.g., temperature and time).

The invented surface-modified molded plastic can be obtained by theaforementioned method and is satisfactory in optical and dimensionalstability and is excellent in adhesion and adhesive property to coatingfilms and in antistatic property.

The invented method for modifying a polymer can introduce a hydroxylgroup or another polar group into a carbon atom constituting the polymerwith an easy operation, by action of the oxygen-atom-containing gas andby catalysis of the imide compound having a specific structure.Accordingly, the invented method can greatly improve electrificationproperty and other characteristics of the polymer or can impart aspecial function to the polymer. The invented method does not requirespecial monomers, and materials for use in the method are not limited tospecific polymers, and therefore the method can be applied to a verywide variety of applications. Especially, the invented method has anadvantage that it can introduce a polar group directly into a carbonatom constituting a non-aromatic group which is in common in hydrophobicpolymers (nonpolar polymers), such as a methylene or methine carbon atomin a principle chain. In addition, the product modified polymer can beproduced in a required amount as occasion demands using polystyrene,polypropylene, and other general-purpose polymers, and the method ishence efficient. The invented method can also introduce a polar groupwithout cleaving a principle chain. Additionally, a desired functionalgroup (polar group) can be introduced in a desired proportion bycontrolling the type and concentration of the reaction gas and reactionconditions (e.g., temperature and time).

The invented modified polymer can be obtained by the aforementionedmethod and is satisfactory in electrification property and othercharacteristics.

The present invention will be illustrated in further detail withreference to several examples below, which are not intended to limit thescope of the invention.

EXAMPLE 1

A polypropylene [FL 100, produced by Grand Polymer Co., Ltd.] washot-pressed and was cut to a predetermined size to thereby yield apolypropylene sheet (10 mm×30 mm×1.0 mm in thickness). The polypropylenesheet was washed with an aqueous surfactant solution and methanolsequentially, and was immersed in a mixture containing 5 mmol ofN-hydroxyphthalimide, 0.05 mmol of acetylacetonatocobalt (II), and 30 mlof acetic acid, and was allowed to stand at 75° C. in an oxygenatmosphere [1 atm (0.1 MPa)] for 4 hours for oxidation treatment.

The contact angle of water and water absorption of the polypropylenesheet prior to and subsequent to the treatment were determined,according to the following methods. The results are shown in Table 1.

Contact Angle of Water

A total of 0.006 cc of pure water was placed dropwise to the surface ofa sample, and the contact angle (deg) of droplet was determined with anautomatic contact angle meter [produced by Kyowa Interface Science Co.,Ltd. under the type of CA-Z].

Water Absorption

A sample was immersed in pure water at 25° C. and was allowed to standfor 24 hours. The ratio of the increment of the weight of the sampleafter 24 hours to a dry weight was determined and was defined as thewater absorption (%).

EXAMPLE 2

A polystyrene [31N, produced by Daicel Chemical Industries, Ltd.] washot-pressed and was cut to a predetermined size to yield a polystyrenesheet (10 mm×30 mm×1.0 mm in thickness). The procedure of Example 1 wasrepeated except that the polystyrene sheet was used instead of thepolypropylene sheet. The contact angle of water and water absorption ofthe sheet prior to and subsequent to the treatment were determined inthe same manner as in Example 1. The results are shown in Table 1.

EXAMPLE 3

A low-density polyethylene [G109, produced by Sumitomo ChemicalIndustries, Ltd.] was hot-pressed and was cut to a predetermined size toyield a low-density polyethylene sheet (10 mm×30mm×1.0 mm in thickness).The procedure of Example 1 was repeated, except that the low-densitypolyethylene sheet was used instead of the polypropylene sheet. Thecontact angle of water and water absorption of the sheet prior to andsubsequent to the treatment were determined in the same manner as inExample 1. The results are shown in Table 1.

EXAMPLE 4

A metallocene-catalyzed polyethylene [Umerit 1520F, produced by UbeIndustries, Ltd.] was hot-pressed and was cut to a predetermined size toyield a metallocene-catalyzed polyethylene sheet (10 mm×30 mm×1.0 mm inthickness). The procedure of Example 1 was repeated, except that themetallocene-catalyzed polyethylene sheet was used instead of thepolypropylene sheet. The contact angle of water and water absorption ofthe sheet prior to and subsequent to the treatment were determined inthe same manner as in Example 1. The results are shown in Table 1.

EXAMPLE 5

A cyclopentadiene-based polymer [ZEONEX 450, produced by Nippon ZeonCo., Ltd.] was hot-pressed and was cut to a predetermined size to yielda cyclopentadiene-based polymer sheet (10 mm×30 mm×1.0 mm in thickness).The procedure of Example 1 was repeated, except that the low-densitypolyethylene sheet was used instead of the polypropylene sheet. Thecontact angle of water and water absorption of the sheet prior to andsubsequent to the treatment were determined in the same manner as inExample 1. The results are shown in table 1.

EXAMPLE 6

A polypropylene [FL 100, produced by Grand Polymer Co., Ltd.] washot-pressed and was cut to a predetermined size to yield a low-densitypolyethylene sheet (10 mm×30 mm×1.0 mm in thickness). The polypropylenesheet was washed with an aqueous surfactant solution and methanolsequentially, was immersed in a mixture containing 5 mmol ofN-hydroxyphthalimide, 0.05 mmol of acetylacetonatocobalt (II), 30 mmolof adamantane, and 30 ml of acetic acid, and was allowed to stand at 75°C. in an oxygen atmosphere [1 atm (0.1 MPa)] for 1 hour for oxidationtreatment.

The contact angle of water and water absorption of the prior to andsubsequent to the treatment were determined e same manner as inExample 1. The results are shown in 1.

TABLE 1 Exam- Contact Angle (deg) Water Absorption (%) ple SheetMaterial Untreated Treated Untreated Treated 1 polypropylene 101.4 90.50.07 0.07 2 polystyrene 83.1 79.8 0.02 0.02 3 low-density 93.2 80.2 0.030.03 polyethylene 4 metallocene- 93.3 80.8 <0.01 <0.01 catalyzedpolyethylene 5 cyclopentadiene- 83.1 75.2 <0.01 <0.01 based polymer 6polypropylene 101.4 88.2 0.07 0.07

Table 1 shows that the plastic sheets oxidized according to the exampleshad an equivalent water absorption but exhibited a greatly decreasedcontact angle of water as compared with those prior to the treatment,indicating that hydrophilicity of the sheet surfaces was improved.

EXAMPLE 7

A mixture containing 3 g of a polystyrene [produced by Daicel ChemicalIndustries, Ltd. under the trade name of “31N”], 5 mmol ofN-hydroxyphthalimide, 0.05 mmol of acetonatocobalt Co(AA)₂, and 30 ml ofchlorobenzene was stirred at 75° C. in an oxygen atmosphere [1 atm (0.1MPa)] for 3 hours.

The resulting reaction mixture was put into methanol for reprecipitationto thereby yield a modified polystyrene. The modified polystyrene wasdissolved in 10 ml of chloroform and was then purified by putting thesolution into methanol for reprecipitation. The purification procedurewas repeated three times to thereby yield about 3 g of an ultimatelypurified modified polystyrene.

The above-prepared modified polystyrene was subjected to infraredabsorption spectrometry (FT-IR) to thereby find a characteristicabsorption of hydroxyl group in the vicinity of 3500 cm⁻¹, indicatingthat hydroxyl groups were introduced into the polymer. FIG. 1 shows aninfrared absorption spectrum of the polystyrene prior to modification,and FIG. 2 shows an infrared absorption spectrum of the modifiedpolystyrene.

Separately, samples were taken from the polystyrene prior to andsubsequent to modification respectively, and were hot-pressed to yield30 mm×50 mm×1 mm sheets. A total of 0.006 cc of pure water was droppedonto the surface of the sheet and the contact angle (deg) of droplet wasdetermined with an automatic contact angle meter [type CA-Z, produced byKyowa Interface Science Co., Ltd.]. The contact angle is an index ofhydrophilicity. The results are shown in Table 2.

EXAMPLE 8

A modified polymer was obtained in the same manner as in Example 7,except that a cyclopentadiene-based polymer [produced by Nippon ZeonCo., Ltd. under the trade name of “ZEONEX 450”] was used instead of thepolypropylene.

The above-prepared modified polymer was subjected to infrared absorptionspectrometry (FT-IR) to thereby find a characteristic absorption ofhydroxyl group in the vicinity of 3500 cm⁻¹, indicating that hydroxylgroups were introduced intothepolymer. FIG. 3 shows an infraredabsorption spectrum of the cyclopentadiene-based polymer prior tomodification, and FIG. 4 shows an infrared absorption spectrum of themodified cyclopentadiene-based polymer.

Each of samples taken prior to and subsequent to modification wasdissolved in chloroform and was subject to solution casting to yield a30 mm×50 mm×0.1 mm sheet. A total of 0.006 cc of pure water was droppedonto the surface of the sheet and the contact angle (deg) of water wasdetermined with an automatic contact angle meter [type CA-Z, produced byKyowa Interface Science Co., Ltd.]. The results are shown in Table 2.

EXAMPLE 9

A total of 10 g of 3,5-dimethyladamant-1-yl methacrylate was dissolvedin 40 ml of toluene, 0.1 g of azobisisobutyronitrile (AIBN) as aninitiator was added to the solution, and the resulting mixture wasstirred at 60° C. for 5 hours for polymerization. The polymerizationsolution was dropped into methanol and was reprecipitated to therebyyield a poly(3,5-dimethyladamant-1-yl methacrylate). This substance waspurified by dissolving in 20 ml of toluene and reprecipitating inmethanol. The purification procedure was repeated twice to yield about 9g of a purified poly(3,5-dimethyladamant-1-ylmethacrylate).Theobtainedpolymerhad an Mn of 21000 and an Mw/Mn of 1.8 in molecularweight.

A modified poly(3,5-dimethyladamant-1-yl methacrylate) was obtained inthe same manner as in Example 7, except that the above-preparedpoly(3,5-dimethyladamant-1-yl methacrylate) was used instead of thepolypropylene.

The above-prepared modified polymer was subjected to infrared absorptionspectrometry (FT-IR) to thereby find a characteristic absorption ofhydroxyl group in the vicinity of 3500 cm⁻¹, indicating that hydroxylgroups were introduced into the polymer. FIG. 5 shows an infraredabsorption spectrum of the poly(3,5-dimethyladamant-1-yl methacrylate)prior to modification, and FIG. 6 shows an infrared absorption spectrumof the modified poly(3,5-dimethyladamant-1-yl methacrylate).

The contact angle (deg) of droplet in samples prior to and subsequent tomodification was determined in the same manner as in Example 8. Theresults are shown in Table 2.

EXAMPLE 10

A purified poly(1-adamantyl acrylate) and a modified poly(1-adamantylacrylate) were prepared in the same manner as in Example 9, except that1-adamantyl acrylate was used instead of 3,5-dimethyladamant-1-ylmethacrylate.

The above-prepared modified polymer was subjected to infrared absorptionspectrometry (FT-IR) to thereby find a characteristic absorption ofhydroxyl group in the vicinity of 3500 cm⁻¹, indicating that hydroxylgroups were introduced into the polymer. FIG. 7 shows an infraredabsorption spectrum of the poly(1-adamantyl acrylate) prior tomodification, and FIG. 8 shows an infrared absorption spectrum of themodified poly(1-adamantyl acrylate).

The contact angle (deg) of droplet in samples prior to and subsequent tomodification was determined in the same manner as in Example 8. Theresults are shown in Table 2.

EXAMPLE 11

A mixture of 3 g of a polystyrene [produced by Daicel ChemicalIndustries, Ltd. under the trade name of “31N”], 5 mmol ofN-hydroxyphthalimide, 0.05 mmol of acetylacetonatocobalt Co(AA)₂, 20mmol of adamantane, and 30 ml of chlorobenzene was stirred at 75° C. inan oxygen atmosphere [1 atm (0.1 MPa)] for 1 hour.

The resulting reaction mixture was dropped into methanol and wasreprecipitated to thereby yield a modified polystyrene. This substancewas dissolved in 10 ml of chloroform and was then purified by addingdropwise to methanol for reprecipitation. The purification procedure wasrepeated three times to yield about 3 g of an ultimately purifiedmodified polystyrene.

The above-prepared modified polystyrene was subjected to infraredabsorption spectrometry (FT-IR) to thereby find a characteristicabsorption of hydroxyl group in the vicinity of 3500 cm⁻¹, indicatingthat hydroxyl groups were introduced into the polymer.

The contact angle (deg) of droplet in samples prior to and subsequent tomodification was determined in the same manner as in Example 7. Theresults are shown in Table 2.

EXAMPLE 12

A mixture of 3 g of a polystyrene [produced by Daicel ChemicalIndustries, Ltd. under the trade name of “31N”], 5 mmol ofN-hydroxyphthalimide, 0.05 mmol of acetylacetonatocobalt Co (AA)₂, 20mmol of adamantane, 25 ml of chlorobenzene, and 5 ml of acetic acid wasstirred at 75° C. in an oxygen atmosphere [1 atm (0.1 MPa)] for 0.5hour. In this connection, a resin was precipitated with the addition ofacetic acid, but the mixture became a homogenous solution as a reactionproceeded.

The resulting reaction mixture was added dropwise into methanol and wasreprecipitated to thereby yield a modified polystyrene. This substancewas dissolved in 10 ml of chloroform and was then purified by addingdropwise into methanol for reprecipitation. The purification procedurewas repeated three times to yield about 3 g of an ultimately purifiedmodified polystyrene.

The above-prepared modified polystyrene was subjected to infraredabsorption spectrometry (FT-IR) to thereby find a characteristicabsorption of hydroxyl group in the vicinity of 3500 cm⁻¹, indicatingthat hydroxyl groups were introduced into the polymer.

The contact angle (deg) of droplet in samples prior to and subsequent tomodification was determined in the same manner as in Example 7. Theresults are shown in Table 2.

TABLE 2 Contact Angle (deg) Example Polymer Unmodified Modified 7polystyrene 83.1 77.5 8 cyclopentadiene-based 80.9 75.5 polymer 9poly(dimethyladamantyl 84.3 80.6 methacrylate) 10 poly(adamantyl 80.578.5 acrylate) 11 polystyrene 83.1 79.5 12 polystyrene 83.1 77.4

Table 2 shows that the polymers modified according to the examples had alargely decreased contact angle of water and an improved hydrophilicity,as compared with those prior to modification.

What is claimed is:
 1. A method for the surface modification of a moldedplastic, comprising the step of immersing a molded plastic in a solventcontaining an imide compound represented by the following formula (1):

wherein R¹ and R² are each, identical to or different from each other, ahydrogen atom, a halogen atom, an alkyl group, an aryl group, acycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group,an alkoxycarbonyl group, or an acyl group, or R¹ and R² are optionallycombined to provide a double bond between the two adjacent carbon atomsto which R¹ and R² are attached or an aromatic or non-aromatic ring; Xis an oxygen atom or a hydroxyl group; and one or two of N-substitutedcyclic imido group represented by the formula:

indicated in the formula (1) are optionally further formed on the R¹,R², or on the double bond or aromatic or non-aromatic ring formed by R¹and R², and introducing an oxygen-atom-containing gas into the solvent.2. A method for the surface modification of a molded plastic accordingto claim 1, wherein said oxygen-atom-containing gas is at least oneselected from the group consisting of oxygen, carbon monoxide, nitrogenoxides, and sulfur oxides.
 3. A surface-modified molded plastic obtainedby treating a molded plastic according to the method of claim 1 or claim2.
 4. A method for modifying a polymer, comprising the step ofdissolving a polymer in a solvent containing an imide compoundrepresented by the following formula (1):

wherein R¹ and R² are each, identical to or different from each other, ahydrogen atom, a halogen atom, an alkyl group, an aryl group, acycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group,an alkoxycarbonyl group, or an acyl group, or R¹ and R² are optionallycombined to provide a double bond between the two adjacent carbon atomsto which R¹ and R² are attached or an aromatic or non-aromatic ring; Xis an oxygen atom or a hydroxyl group; and one or two of N-substitutedcyclic imido group represented by the following formula:

indicated in the formula (1) are optionally further formed on the R¹,R², or on the double bond or aromatic or non-aromatic ring formed by R¹and R², and introducing an oxygen-atom-containing gas into the resultingsolution.
 5. A method for modifying a polymer according to claim 4,wherein said oxygen-atom-containing gas is at least one selected fromthe group consisting of oxygen, carbon monoxide, nitrogen oxides, andsulfur oxides.
 6. A modified polymer obtained by treating a polymeraccording to the method of claim 4 or claim 5.